Lack of histological cerebellar changes in Wistar rats given pulegone for 28 days. Comparison of immersion and perfusion tissue fixation

Pulegone was given orally by gavage to groups of 28 SPF Wistar rats at dosage levels of 0 or 160 mg/kg body weight per day for 28 days. Clinically treated animals showed slackness, depression, decreased food consumption, and body weight. The loss of body weight was accompanied by a marked decrease in plasma creatinine. In contrast to earlier results, this study did not reveal occurrence of cyst-like spaces in the white matter of cerebellum using either perfusion or immersion tissue fixation techniques. Pulegone increased plasma alkaline phosphatase and relative liver weight indicating an adverse effect on the liver.

Steady-state pharmacokinetics of the enantiomers of citalopram and its metabolites in humans

The steady-state pharmacokinetics in serum and urine of the enantiomers of citalopram and its metabolites, demethylcitalopram (DCT) and didemethylcitalopram (DDCT), were investigated after multiple doses of rac-citalopram for 21 consecutive days (40 mg per day) to healthy human subjects who were extensive metabolisers of sparteine and mephenytoin. Comparable pharmacokinetic variability was noted for (+)-(S)-, (-)-(R)- and rac-citalopram. Enantiomeric (S/R) serum concentration ratios for citalopram were always less than unity and were constant during the steady-state dosing interval. A modest, but statistically significant, stereoselectivity in the disposition of citalopram and its two main metabolites was observed. Serum levels of the (+)-(S)-enantiomers of citalopram, DCT, and DDCT throughout the steady-state dosing interval investigated were 37 +/- 6%, 42 +/- 3% and 32 +/- 3%, respectively, of their total racemic serum concentrations. The (+)-(S)-enantiomers of citalopram, DCT, and DDCT were eliminated faster than their antipodes. For (-)-(R)- and (+)-(S)-citalopram, respectively, the serum t1/2 averaged 47 +/- 11 and 35 +/- 4 h and AUCss averaged 4,193 +/- 1,118 h.nmol/l and 2,562 +/- 1,190 h.nmol/l. The observed enantiospecificities were apparently more related to clearance, rather than to distributional mechanisms.

A phase III double-blind randomised study of rectal sucralfate suspension in the prevention of acute radiation proctitis

BACKGROUND AND PURPOSE

A limited number of studies have suggested that oral sucralfate reduces the acute and late gastro-intestinal side-effects of pelvic radiotherapy and sucralfate enemas ameliorate symptoms of chronic proctitis. Sucralfate may act via local bFGF at the mucosal level in promoting angiogenesis and reducing epithelial associated microvascular injury. This multi-institutional study was designed to test the hypothesis that sucralfate given as an enema would have a significant protective effect against acute radiation induced rectal injury by direct application to the mucosa.

MATERIALS AND METHODS

Eighty-six patients having radiotherapy for localised carcinoma of the prostate were randomised in a double-blind placebo-controlled study to receive either 15 ml of placebo suspension or 3 g of sucralfate in 15 ml suspension, given as a once daily enema during and for 2 weeks following radiotherapy. Assessment was based on the EORTC/RTOG acute toxicity criteria and a patient self-assessment diary.

RESULTS

There was no significant difference between placebo and sucralfate for peak incidences of EORTC/RTOG proctitis. For the placebo and sucralfate arms 95 and 88% (difference 7 +/- 11%) suffered some degree of proctitis, with 71 and 61% (difference 10 +/- 19%) reaching grade 2, respectively. The median period to onset of grade 2 proctitis was 33.5 and 36 days, with the median duration being 9.5 and 15 days, respectively, again these difference being non-significant. Thirty-five and 37% of patients rated the effect of radiotherapy on bowel habit as 'a lot' with a moderate or severe effect on normal daily living in 52 and 49%, respectively.

CONCLUSION

This study suggests that sucralfate given as a once daily enema does not substantially reduce the incidence of symptoms associated with acute radiation proctitis and its routine clinical use cannot be recommended. This cohort of patients will be followed to determine if any difference develops in relation to late toxicity.

Mucosal regeneration during radiotherapy. Trans Tasman Radiation Oncology Group (TROG)

BACKGROUND AND PURPOSE

Regeneration of the aerodigestive mucosa is known to occur during conventionally fractionated radiotherapy. The circumstances surrounding its time of onset and magnitude are not well understood, however.

MATERIAL AND METHODS

Mucosal reactions were observed in 100 patients undergoing conventionally fractionated treatment at 2 Gy/day over 7 weeks and 88 receiving accelerated treatment at 1.8 Gy twice daily over 3 1/2 weeks on the Trans Tasman Radiation Oncology Group head and neck cancer trials. Similar observations in 61 patients treated palliatively at dose rates between 0.8 and 240 Gy/h using ten 3.0-4.2 Gy fractions over 2 weeks are compared.

RESULTS

Several findings emerged from these studies: 1. Reactions evolved more quickly at oropharyngeal sites than in the hypopharynx. 2. Reactions at both sites evolved more rapidly at greater rates of dose accumulation. 3. The timing of reactions suggested the presence of a strong regenerative mucosal response that started before the manifestation of "patchy' (grade II) mucosal reactions. 4. The regenerative response was strong enough to "make good' damage accumulated at a rate of 2 Gy/day in over a third of cases. 5. The linear quadratic model without time correction failed to provide an adequate prediction of the frequency or intensity of mucosal reactions produced by any of the regimes. A simple model of the regenerative response is presented.

CONCLUSIONS

This study suggests that the timing and magnitude of the regenerative response vary between sites and individuals but are linked to the amount of epithelial cellular depletion occurring during treatment.

City air pollution of polycyclic aromatic hydrocarbons and other mutagens: occurrence, sources and health effects

The presence of polycyclic aromatic hydrocarbons (PAH), mutagens and other air pollutants was investigated in a busy street in central Copenhagen and in a park area adjacent to the street. The winter concentration of benzo(a)pyrene was 4.4 +/- 1.2 ng/m3 in the street air and 1.4 +/- 0.6 ng/m3 in the city park. The atmospheric concentrations of PAH decreased in the order of: street > city background air approximately suburbs > village > open land. The traffic contribution of PAH to street air was estimated to be 90% on working days and 60% during weekends and its contribution to city background air was estimated to be 40%. Four different approaches to evaluate the health effects are discussed. The direct effect of PAH air pollution, and other mutagens, is considered to be a maximum of five lung cancer cases each year out of one million people.

Is surgery necessary in stage III and stage IV cancer of the head and neck that responds to induction chemotherapy?

OBJECTIVE

To study the influence of surgery in patients who achieve a response to induction chemotherapy.

DESIGN

Nonrandomized retrospective study.

SETTING

Comprehensive cancer center.

PATIENTS

The records of all patients with state III and stage IV squamous cell carcinoma of the oral cavity, oropharynx, and hypopharynx were reviewed at the Queensland Radium Institute, South Brisbane, Australia, in the years 1970 through 1990.

INTERVENTIONS

There were 314 patients where induction chemotherapy was used as part of a curative treatment. Complete response occurred in 20 patients, partial response in 110 patients, nonresponse in 162 patients, and unknown response in 22 patients. To assess the impact of surgery, the responders were divided into two treatment groups: one group (n = 57) received chemotherapy surgery, and radiotherapy (C/S/XRT), and a second group (n = 73) received chemotherapy and radiotherapy (C/XRT).

MAIN OUTCOME MEASURES

Five-year survival, local failure, nodal failure, and distant failure.

RESULTS

The 5-year actuarial survival for the chemotherapy responders and nonresponders was 58% and 43%, respectively (P < .05). When analyzed by treatment group, those receiving C/S/XRT had a 65% 5-year survival (95%) confidence intervals [CIs], 53 to 78) and those receiving C/XRT had a 56% 5-year survival (95% CI, 44 to 70). However, when the complete responders were assessed, those receiving C/S/XRT had a 90% 5-year survival (95% CI, 72 to 99) vs a 51% survival (95% CI, 18 to 89) for those treated with C/XRT. For the partial responders, the survival for the groups C/S/XRT and C/XRT were 59% (95% CI, 45 to 79) and 53% (95% CI, 41 to 67), respectively. Chemotherapy responders were less likely to fail locally if they were treated with C/S/XRT than with C/XRT (21% vs 43%, P < .01).

CONCLUSION

The results suggest that surgery still has a role to play in patients who achieve a response with chemotherapy, even when the response is complete.

Radiation therapy for nodal disease in malignant melanoma

Radiation therapy has been widely used for palliative management of inoperable metastatic malignant melanoma. For patients with nodal disease, response rates of approximately 70% have been reported. There are limited data concerning the role of adjuvant irradiation following therapeutic lymph node dissection. In this review, 57 patients with isolated resectable and nonresectable nodal disease have been treated with radiation. The overall response rate is 84% for bulky disease. Large fractions are beneficial. The median disease-free survivals were 11 months after adjuvant treatment and 7 months for those with inoperable disease. The median overall survivals were 20 months and 18 months, respectively. Local control in long-term survivors was excellent. Sixty-five percent of patients developed distant metastases. There is a need for additional studies with the use of adjuvant radiation therapy following lymph node dissection.

Radiation therapy for squamous cell carcinoma of the nasal vestibule

PURPOSE

A retrospective review of carcinomas of the nasal vestibule seen at the Queensland Radium Institute over a 30-year period was undertaken.

METHODS AND MATERIALS

Twenty-nine patients with squamous cell carcinoma of the nasal vestibule who were treated with curative intent between 1960 and 1989 were analyzed. The 5-year actuarial survival and disease-free survival were 64% and 61%, respectively.

RESULTS

Seven patients were treated with combined modality treatment using surgery and post-operative radiotherapy and 22 were treated with radiation alone. The ultimate local control for those treated with combined modality treatment was 66% and for those treated with radiation alone was 68%. The 5-year actuarial survival was 57% and 67%, respectively.

CONCLUSION

In view of the similar local control rates and 5-year survival in the two groups, we suggest that combined modality treatment may not be warranted in the initial treatment of patients with these tumors. Radiation treatment alone with salvage surgery would appear to be the treatment of choice.

Triple therapy for advanced squamous cell cancer of the head and neck

This study presents the results of treatment for Stage III and IV squamous cell carcinoma of the head and neck at the Princess Alexandra Hospital and Queensland Radium Institute, Brisbane. Patients were treated using a programme of sequential chemotherapy, surgery and radiotherapy. Between 1980 and 1988, 116 patients commenced the programme and 85 completed the treatment as planned. The Price-Hill regimen of chemotherapy was used until 1986 after which time it was replaced by cisplatin/5-fluorouracil (5FU). Two courses were usually given achieving an overall response rate of 36% (12% complete response). Cisplatin/5FU produced an overall response rate of 56% compared with 24% for the Price-Hill regimen. Radical surgical resections were performed using a free flap reconstruction in the majority of patients. Radiotherapy fields usually covered the primary site and both cervical lymph node areas to a dose of 50-60 Gy in 5-6 weeks. The lengthy treatment was generally well tolerated although there were two chemotherapy and two perioperative deaths. The overall actuarial survival for the 85 patients completing the triple therapy was 60%. These patients were analysed in more detail for possible prognostic factors.

Passive sensitization and histamine release of basophils. IgE and cellular factors regulating histamine release

This study had two purposes. First, to examine a possible functional heterogeneity of IgE regulating basophil histamine release and the effect of using two different donor cells for passive sensitization experiments. Second, to investigate basophils not releasing histamine to anti-IgE by stimulating protein kinase C with the addition of the phorbol-ester, TPA. In consecutive experiments responding donor basophils were passively sensitized with plasma from non-responding subjects. Thus, the first set of experiments included passive sensitization of acid treated donor basophils from one atopic and one non-atopic patient with plasma from 29 children with exogenous asthma to grass pollen, cat dander, or dust mites. Different secretagogues (anti-IgE, Concanavalin A, and N-formyl-methionyl-leucyl-phenylalanine) induced different histamine release responses due to a cellular property of the basophils not related to the type of IgE bound to the cell membrane. It was demonstrated that the allergen-induced histamine release did not depend on the extract or type of IgE when the biological activity of each extract and serum-specific IgE levels were similar. However, the atopic donor cells released significantly (P less than 0.05) more histamine than non-atopic donor cells. Thus, histamine release depends on the type of secretagogues and a cellular property which is maybe influenced by the presence of serum factors and a certain type of IgE in the serum of atopics. The second set of experiments included 10 patients (6 atopics and 4 non-atopics) with non-histamine releasing basophils. In the presence of 10 ng/ml TPA, however, seven of 10 patients released histamine at anti-IgE challenge. Three months later two additional patients became responsive in the presence of TPA. By passive sensitization of responding donor basophils the non-responding patients were shown to possess functionally intact IgE. Thus, the discrepancies sometimes observed between clinical symptoms, serological IgE-antibody measurements and histamine release testing in allergic patients may be related to a cellular property of basophils.

Nitrosamine carcinogen activation pathway determined by quantum chemical methods

Multiple reactions are thought to be involved in transforming dialkynitrosamines to active carcinogens. The first proposed step is enzymatic alpha-hydroxylation by the active oxygen species of cytochrome P-450, followed by nonenzymatic N-dealkylation and formation of diazohydroxides (RNNOH). The latter transformation can reasonably occur by a two-step mechanism via tautomerization of a monoalkylnitrosamine intermediate or directly from the alpha-hydroxylated species in one step. Both of these pathways in the transformation of hydroxymethylnitrosamine to diazohydroxide and formaldehyde were examined by the semiempirical molecular orbital method MNDO (modified neglect of diatomic differential overlap) and the ab initio method using STO-3G and 3-21G basis sets. Complete geometry optimizations of all reactants, intermediates, transition states, and products were performed. MNDO was also used to compare the similar transformation of the dimethyl analog. Both methods show that in the gas phase a concerted pathway involving a six-membered ring transition-state pathway is kinetically favored over a two-step pathway involving N-demethylation followed by tautomerization via two four-membered ring transition states. This reaction appears to be a viable one to formation of an ultimate carcinogen by parent dialkylnitrosamines in the hydrophobic substrate binding site of cytochrome P-450.

Dementia of the Alzheimer's type and depression

This retrospective review of medical records was designed to address three questions: 1) Can the depression seen in some patients with Dementia of the Alzheimer's Type (DAT) be successfully treated? 2) Does this treatment lead to any long-term improvement in the patient's cognitive status? and 3) Do patients with coexisting DAT and depression have a different long-term clinical course than nondepressed DAT patients? In the authors' sample of 131 DAT subjects, 41 (31%) also met DMS-III criteria for a major affective disorder. Of those DAT plus depression patients whose records reflected treatment (usually with a tricyclic antidepressant), 85% (17 of 20) showed clear evidence of improvement in mood, vegetative signs, or activities of daily living (ADLs) based on review of the medical record. An analysis of change in cognitive function (measured by the Folstein Mini-Mental State) and five global measures failed to reveal any differences between the depressed and nondepressed groups after a mean interval of 17 months. The depression that occurs in approximately one-quarter to one-third of DAT patients appears to respond to appropriate therapy. These patients often show improvement in their mood and ADLs but remain demented.

Computer-assisted mechanistic structure-activity studies: application to diverse classes of chemical carcinogens

In the first part of this paper we have indicated how the techniques and capabilities of theoretical chemistry, together with experimental results, can be used in a mechanistic approach to structure-activity studies of toxicity. In the second part, we have illustrated how this computer-assisted approach has been used to identify and calculate causally related molecular indicators of relative carcinogenic activity in five classes of chemical carcinogens: polycyclic aromatic hydrocarbons and their methyl derivatives, aromatic amines, chloroethanes, chloroalkenes and dialkyl nitrosamines. In each class of chemicals studied, candidate molecular indicators have been identified that could be useful in predictive screening of unknown compounds. In addition, further insights into some mechanistic aspects of chemical carcinogenesis have been obtained. Finally, experiments have been suggested to both verify the usefulness of the indicators and test their mechanistic implications.

Theoretical structure-activity studies of benzodiazepine analogues. Requirements for receptor affinity and activity

Conformational and electronic properties of a series of 1,4-benzodiazepine analogues and their specific interaction with a model cationic receptor site have been calculated using both empirical energy and semiempirical molecular orbital methods. The aim of these studies was to identify molecular properties and modes of receptor interaction which are determinants of relative receptor affinities and pharmacological activities for these anxiolytics. Analogues with variations in key positions of the 7-membered (B) ring, at positions C7, C8, and C9 of the fused phenyl (A) ring, and at positions 2' and 4' of the phenyl (C) ring were examined. The results indicate that both active and inactive analogues have similar low-energy conformations, arguing against this property as a modulator of recognition at the receptor. However, calculated molecular electrostatic potentials together with explicit model receptor interactions allowed the deduction that interactions with three cationic receptor sites are required for high-affinity analogues. The specific cationic site interactions are postulated with electron-withdrawing groups at C7, the C2 = O1 group, and the imine nitrogen, N4. Moreover, interactions of N4 with a model cationic receptor site are enhanced by halogen substituents at C2', but only when the phenyl ring is rotated by 30 degrees toward a more planar conformer, corresponding to an induced conformational change. If this enhancement is important, a 2'-Cl substituent on more rigid analogues of the 1,4-benzodiazepines with increased co-planarity of the phenyl C-ring and the C1'--C5 = N4 plane should have an even greater differential effect on receptor affinity.

Metabolism and relative carcinogenic potency of chloroethanes: a quantum chemical structure-activity study

Using the all-valence electron, semiempirical molecular orbital method, MNDO, properties have been identified and calculated for eight chloroethanes which can serve as indicators of their extent of transformation to alcohols by cytochrome P450 and the subsequent formation of aldehydes by loss of HCl from these alcohols. The assumption was made that these aldehydes are the active carcinogens of the chloroethanes and that they act as electrophiles in adduct formation with DNA bases. Electrophilic properties of these putative ultimate carcinogens have been calculated which are indicators of the rank order of carcinogenic activity of the parent compounds in susceptible species. Particularly relevant in this respect are (a) the electron affinity of aldehydes as measured by the energy of their electron accepting (lowest energy virtual) orbital, and (b) the net charge on the C alpha carbon, adjacent to the carbonyl carbon, which can participate in electrophilic attack on nucleophilic sites of DNA bases. The molecular properties identified in this study as indicators of rank order or carcinogenic activity of the parent chloroethanes are consistent with the importance of cytochrome P450 in transforming halohydrocarbons to active carcinogens and of acylchlorides and chloroaldehydes as the active form. Their validity and usefulness can be further tested in screening unknown and more complex chlorohydrocarbons for carcinogenic activity.

Quantum chemical studies of methylbenz[a]anthracenes: metabolism and correlations with carcinogenicity

In the context of the bay region, K-region and radical cation hypotheses for polycyclic aromatic carcinogens, molecular properties were calculated for fourteen methyl derivatives of benz[a]anthracene (BA) related to (1) intrinsic substrate reactivities towards activating and detoxifying metabolism and (2) the stabilities of the putative carbocation ultimate carcinogens. All-valence electron methods were used, avoiding the inherent difficulties found in the pi-electron methods. The calculated substrate reactivities were found to predict major metabolites successfully, supporting the validity of their use in attempted correlations with observed carcinogenic potencies. Positive correlations were found between observed carcinogenic potencies smf (1) the reactivities of the parent polycyclic aromatic hydrocarbons (PAH) towards the initial distal bay region epoxidation and (2) the stabilities of the diol epoxide carbocations. This latter correlation holds when both the methyl derivatives of BA and previously studied unsubstituted PAH are considered together, indicating its potential usefulness as a screening parameter for carcinogenic activity.